Absorption refrigeration



March 17, 1953 s, BACKSTROM 2,631,443

ABSORPTION REFRIGERATION Filed Feb. 26, 1949 2 SHEETS-SHEET l jINlfENTOR. A9 I 3-? 'BY M Patented Mar. 17, 1953 UNITED STATES OFFICEABSORPTION REFRIGERATION SigurdMattias Backstrom; Stockholm. Sweden,assignor to Aktiebolaget Elektrolu-x, Stockholm, Swedema corporation: ofSweden.

ApplicationFbruary 26, 1949, Serial No. 78,511 In Sweden March 2, .1948

81ClaimSr (Cl; GEM-119.5)-

and accumulate on such-lowtempera-ture cooling element.

Another object of my invention 'is to provide an improved refrigeratorin which an absorption refrigeration system having one or more coolingelements is employed for maintaining a freezing section-at a desired lowtemperature,

and utilizing such refrigeration systemto effect coolin of athermallysegregatedspace with the aid .of a secondary heat transfersystem in such manner that, whenheatis suppliedto the cooling. element.or elements of the freezing section:

to meltfrost whichxmay form thereon, substantially no heat is suppliedto the evaporationportion. of. the secondaryheat transfer system.arranged. to: abstract h-eat'sfrom such other space.

The novel features which Lbelieve to :becharacteristic of my inventionare set forth with .particularity in the claims. The invention, both asto organization and method, together with the above and other objectsand advantages thereof, will be better understoodby reference tothefollowing description taken in connection with the accompanying drawingsforming a part of this specification, and of which Fig. 1 more. or lessdiagrammatically illustrates anabsorption refrigeration system embodyingthe invention; Fig. 2 isan enlarged fragmentary sectional view taken atline 2-2 of Fig. 1.; and Fig. .3isavvertical sectional view of arefrigerator cabinet schematically illustrating one manner in whichparts of the refrigerationsystemof Fig. 1. may be incorporated thereinin accord withthe invention.

In'Fi'g. 1 I have shown my invention inconnection with anabsorptionrefrigeration system of a uniform pressure type which is wellknown in the art and in which an inert pressure'equalizing gas isemployed. Such a refrigeration system comprises a generator or vaporexpulsion unit'ia including a boiler or pipe ll containing. arefrigerant, such as'ammonia, in a bodyoi absorption liquid, such aswater. 'Heat issupplied to the boiler" l them a heating tube or'fiue l2thermally connected therewith, as by welding, forexample; The heatingtube i2 may be heated in any suitable manner, as by an electricalheating element disposed within the lower part of the tube-l2 or by aliquid or gaseous fuel burner which is adapted to project its flame intothe-lower heat input 'end of the'tube.

The heat supplied to the boiler H and its contents expelsrefrigerant'vapor out of solution and such vapor passes upwardly from the'vaporexpulsion uni-t H! into air cooled condensers l5 and I in which. it iscondensed and liquefied. Liquidrefrigerant flows from condensers ltzandll through conduits-t8- and it into cooling elementsor eVapQratOrs'Z-EBand 2!, respectively, in

which it evaporates and diffuses into an inert pressure equalizing gas,such as hydrogen, which enters througha conduit 22.. Due to evaporationof refrigerant'fiuid into inert .gas, a refrigerating effect is-producedby cooling elements 20 and 2| with consequent. absorption of heat fromthe surroundings.

The rich .gas mixture .of refrigerant vaporiand inert gas formed incooling elementszZfl and 2| merge or come together at 2%.andflowsthrougha. conduit 24, one passage of a gas heat exchanger 25, conduit'zliv andabsorber'vessel. 21 intothe lower endof an absorber coil 28. In absorbercoil 28 therich gas mixture flows counter-current to. downwardly flowingabsorption liquidwhich enters-through.a.conduit 29. The

absorption liquid absorbsref-rigerant vapor from inert.gas,.andinertlgasweak in refrigerant flows from absorber coilzZB .in apathof flowincluding conduit 5d, another passage of gas heat exchanger 25'andconduit ZZ-into the upper parts of the cooling elements 20 and 2-1.

Absorption solution enriched in refrigerant flows from the absorbervessel 2-7 through a conduittl andaninner passage .iZofla liquidiheatexchanger 33- into the lower end ofa lift tube or pump pipe 3 6. Thepump pipe-3 lisin thermal exchange relation with the heating tube 82,as-by welding, for example, and liquidis raised therethroughbyvapor-liquid lift action to the upper partofthe boiler I-l.The-vapor'expelled out of solution in-boiler H, together with vaporentering-the latter from the pumppipe 3 1 flows upwardly'from the-vaporexpulsionunit 10 to the condensers lt'and H; as previously explained.Theabsorption liquid from which refrigerant has been expelled flows fromthe boiler ll through the-outer passagetfi of theliquid heat 3 exchanger33 and conduit 29 into the upper part of the absorber coil 28.

The outlet ends of the condensers l6 and I! are connected by a conduit36, vessel 31 and conduit 38 to a part of the gas circuit, as at one endof gas heat exchanger 25, for example, so

that any inert gas which may pass through the condensers I6 and I! canflow into the gas circuit. Refrigerant vapor not liquefied in thecondensers flows through conduit 36 to displace inert gas in vessel 31and force such gas through conduit 38 into the gas circuit. The effectof forcing gas into the gas circuit in this manner is to raise the totalpressure in the entire system whereby an adequate condensing pressure isobtained to insure condensation of refrigerant vapor in condensers I6and II.

The vessel 31 in effect serves as an extension of the air cooledcondensers l6 and H. Refrigerant condensed in the vessel 31 flowstherefrom through conduit 36 at the lower end of which a liquid dividermay be provided in any suitable manner. As shown in Fig. 2, the lowerend of conduit 36 may be formed with branches or arms 39 at the upperends of which a baffle or divider 40 is disposed to divide any liquidflowing downwardly in conduit 36 into two streams, one of which isconducted through conduit l8 to cooling element 20 and the other throughconduit H) to the cooling element 2|.

In order to increase the temperature of cooling elements 2|) and 2| whenit is desired to melt frost which may accumulate thereon, provision ismade for raising warm absorption solution from the boiler through ariser conduit 4| into the vessel 31. The raised warm absorption solutionflows from vessel 3? through conduit 36, such solution being dividedinto two streams at the lower end of conduit 36 and passing into thecooling elements 26 and 2|. In this manner rapid defrosting is efiecteddue to the relatively high temperature to which the solution is heatedin the vapor expulsion unit H3. The absorption solution passes from thecooling elements through conduit 24 and gas heat exchanger 25 to theabsorber vessel 21.

The riser conduit 4| constitutes a vapor lift tube or pump pipe throughwhich absorption solution is raised when desired by heat derived fromthe heating flue |2 with the aid of a controllable secondary heattransfer system. As shown in Fig. 1, such a system may include avertical conduit 43 and a U-tube 44 having one arm connected to thelower end of conduit 43 and the other longer arm 46 in thermal relationwith the heating tube |2 at 46. The upper part of the arm 45 is also inthermal relation with the riser conduit 4| at 41, and the extreme upperend thereof is connected to the upper part of conduit 43. A bulb 48 isflexibly connected at 49 to the upper end of the conduit 43.

The heat transfer system is hermetically sealed and is charged with avolatile fluid substantially all of which is held in the bulb 48 whenthe latter is in the position shown in Fig. 1. When it is desired toeffect defrosting of the cooling elements 23 and 2|, the bulb 48 israised from the position shown, so that fluid will flow therefrom bygravity to the U-tube 44. The longer arm 45 of the U-tube 44 constitutesthe vaporization portion of the heat transfer system in which fluid isvaporized by heat taken up from the heating tube l2. The vapor formed inthis manner is partly condensed in the arm 45 and gives up heat to theconduit 4| and its contents to raise absorption,

solution by vapor lift action from the boiler II to the vessel 37. Suchlifting of absorption solution continues until all of the vapor iscondensed in the bulb 4-8 which previously has been returned to itslower position shown in Fig. 1. In this way substantially all of thevolatile fluid is held back from the lower vaporization portion of arm45, and heat transfer to the conduit 4| is reduced to terminate raisingof solution therein.

In Fig. 3 is shown a refrigerator comprising a cabinet 59 havingthermally insulated walls defining a storage space 5|. In the upper partof space 6| is provided a freezing section comprising a shell 52 havingthermally insulated walls defining a chamber 53 within which the coolingelements 26 and 2| of the refrigeration system of Fig. l are disposed.Although not shown, it is to be understood that closure members or doorsare provided to close an access opening of the space 5| and a similaraccess opening of the chamber 53.

One of the coolin elements 26 may be employed for ice freezing andprovided with suitable supporting surfaces upon which ice trays 54 canbe positioned. The other cooling element may be employed primarily tocool the freezing chamber 53 in which frozen foods, meat and othermatter may be stored. Hence, it is desirable to insulate the chamber 53effectively from the storage space 5|.

The parts of the refrigeration system shown in Fig. 2 are similar tothose illustrated in Fig. 1, like parts being indicated by the samereference numerals. In the operation of the refrigerator of Fig. 2,liquid refrigerant is conducted to the upper parts of cooling elements26 and 2| through conduits l8 and I3, respectively, as previouslyexplained in describing the refrigeration system of Fig. l. Inert gasweak in refrigerant flows from the absorber through conduit 36, onepassage of gas heat exchanger 25 and conduit 22 whose upper endcommunicates with the upper ends of cooling elements 2|] and 2|.Refrigerant evaporates and diffuses into inert gas in the coolingelements 26 and 2|, and such gas mixture from the cooling elements 26and 2| merge at 23. All of the gas mixture then flows through theconduit 24, one passage of the gas heat exchanger 25 and conduit 26 tothe absorber. Any unevaporated refrigerant also flows from the coolingelements 26 and 2| and meet at 23 from which region all of therefrigerant flows through conduit 24 and gas heat exchanger 25 andeventually finds its way to the absorber vessel.

In accordance with my invention the absorption refrigeration systemhaving the cooling ele ments 26 and 2| is advantageously employed toeffect cooling of storage space 5i with the aid of a secondary heattransfer system 55 which is so arranged that, when heat is supplied tothe cooling elements 20 and 2| to melt frost accumulated thereon,substantially no heat is supplied to the evaporation portion of thesecondary heat transfer system which is arranged to abstract heat fromthe storage space 5|.

The secondary heat transfer system 55 includes an evaporation orvaporization portion 56 in the form of piping which desirably isdistributed thermal exchange relation with the conduit 24,

as by a plurality of heat transfer plates or fins 53, for example. Theheattransfer system 55 is herego-321,443

'n'q'etically sealed and ispartly filled'with a suitable 'volatilefluidor heat transfer agent having a relatively lowboiling temperature.In certain instances the heat-transfer system 55 may also bechargediwith asuitable quantity of inert gas in: addition to thevolatile heat transfer fluid.

During operation of the refrigerator the volatile fiuid-evaporates inthe lower part of the vaporization-portion eie and also partly in thevertically extendin partsthereof, thereby taking up heat fromair in thestorage space 54. To promote such taking-up ofheat from the storagespace oi, the vaporization'portion 56 desirably is provided with-heatabsorbing members to provide a relatively extensive heat transfersurface. The vapor flows from the vaporization portion 53 tothe-condensation portion 5-7 in which the vapor ifs-condensed andliquefied, such condensate then returning by gravity to the vaporizationportion 56.

The heat ofcondensation resulting from condensa-tion of vapor in thecondensation portion is given up to fluid flowin through the conduit 24: Since the gas mixture formed in the cooling elements wand 21andpassing through the conduit 2 1* is relatively cold, such gas mixturecan be effectively utilized to take up the heat of condensationresulting from condensation of vapor in the' condensation portion 5? ofthe secondary 'heattransfer system. When unevaporated refrigerant fromthe cooling elements 29 and 22 flows through the conduit 24', the latterin effect acts as an auxiliary cooling element in whichrefrigerantevaporates and diffuses into inert gas, thereby effectivelytaking up heat of condensation libera't'ed by the secondary heattransfer system.

Itwill now be understood that therefrigeration system of which thecooling elements so and 2i form a part is employed to cool storage space5% with-the aid of'the secondary heat transfer system 55. With sucharrangement the storage space 5 is maintained at a useful refrigeratingtemperature which, however, is higher than that at whichthe freezingchamber 53 is maintained by the cooling elements 2i! and ill.

Theconduit 2 3, condensation portion 5'? of the secondary heat transfersystem 55 and heat trans- 'fer plates 58 thermally connecting theseparts essentiallyconstitute a heat exchanger. In order to obtainefficient operation of such heat exr changer and take full advantage ofconduit as and thefluids il'owing therethrough to take up heat ofcondensation, the conduit 2%, condensa- 'tion portion 5'! and plates 58desirably are emrbeddedin a body of suitable insulating material,asindicated at (it in Fig. 3.

During defrosting periods Warm absorption solution'is supplied tocooling elements it and '21 to melt frost thereon, as previouslyexplained.

' f Su'ch absorption solution passes from cooling eleents 2'3 and 2!through conduit 24 and gas heat exchanger 25 and eventually finds itsway to the absorber vessel. Under such conditions the temperature ofconduit-2e rises sufficiently so that condensation of vapor can nolonger take place inthe condensation portion of the secondary heat"transfer system. When this occur the natural circulation of volatilefluid in the heattransfer system 5'5 stops, and heat temporarily is notabstracted from the storage space 5%. Under these conditions the body ofinsulation disposed about the conduit 24 thermally shields the latterfrom the storage space 5!, so that the increase in temperature in thespace 5| due to how of absorption solution through-theconduit 21i isnegligible and 6 only dependent upon the extent of heatleakage throughthe insulation Although not shown, it is also advantageous for thereasons justgiven to embed the gasheat exchanger 25 in suitableinsulation when the latter is. located .inthe storage space 5 l, asillustrated in Fig. 3.

In view-of the foregoing, itwiil now be understood thatwhen heat issupplied to cooling elements 2i! and 2! to effect defrosting, no heat toany appreciable" extent is supplied. to the vaporization portion atemployed to effect cooling of the higher temperature storage space 5i.Since f-rostonly forms and accumulates on the low temperature coolingelements employed for freezing purposes, and substantially no frostforms inla higher temperature cooling space like the spaceifiii in Fig.3 by reason of the relatively extensive heat transfer surface providedto abstract heat there'- from, it is of distinct advantage to supplydefrosting heat only to the cooling element or elements upon which frosttends to form audaccumulate, thereby making it possible to continue tostore food and other matter at a safe refrigerating temperature in thehigher temperature storage space which frost normally does not form andaccumulate.

Modifications of the embodiment of my inventi n which I havedescribedwill occur to those slcilled in the art, so that I desire myinvention not to be limited to the particular arrangement forth. Forexample, provision may be. made supply a heating fluid other than warmabsorption solution to the cooling element or elements upon which frosttends to form. Thus, refrigerant vapor flowin from the generator unitmay be arranged to pass directly into one or more cooling elements in aheated state to eifect defrosting. Also, the inner liner definin thespace with which the secondary heat transfer system is associated may bedouble-walled to provide a space therebetween which can be employed asthe vaporization portion of the secondary heat transfor system, therebyavoiding the necessity of providing a vaporization portion formed oftubing or piping. Therefore, I intend in the claims to cover all thosemodifications which do not depart from the spirit and scope of myinvention.

What is claimed is:

1. In a refrigerator comprising a cabinet having segregatedcompartments, an absorption refrigeration system including an absorptionsolution circuit and a gas circuit comprising an absorber and one ormore cooling elements in which refrigerant fluid evaporates in thepresence of an inert gas and conduit means for conducting inert gasenriched in refrigerant from the latter to said absorber, at least oneof said cooling elements being arranged to abstract heat from one ofsaid compartments which is employed for freezing purposes and may causeformation of frost due to the refrigerating effect produced thereby, asystem for heat transfer iiuid having a vaporization portion arranged toabstract heat from another of said compartments and a heatrejecting'portion in heat conductive relation with said conduit means,said refrigerationsystem including means for supplying warm absorptionsolution to said one cooling element which is operable to cause meltingof any frost which may be formed, said conduit means serving to conductsuch absorption solution from said one cooling element to saidabsorption solution circuit, and said conduit means at the region saidheat rejecting portion is in heat conductive relationtherewith beingthermally segregatedfrom said other compartment, said heat conductiverelation being so constructed and formed that any increase intemperature of said other compartment resulting from flow of absorptionsolution through said conduit means is substantially negligible.

2. A refrigerator as set forth in claim 1 in which said heat rejectingportion is in heat conductive relation with a portion of said conduitmeans disposed in said other compartment.

3. A method of refrigeration which includes evaporating a firstrefrigerant fluid in the presence of an inert gas in one or more placesof vaporization thermally segregated from the surroundings to producerefrigeration which may cause the formation of frost, flowing relativelycool inert gas enriched in refrigerant from the first-mentioned place orplaces of vaporization in a path of flow to a region removed therefromwhich is at a lower level and serves as an auxiliary place ofvaporization, flowing excess unevaporated refrigerant by gravity in suchpath of flow to said auxiliary place of vaporization from thefirst-mentioned place or places of vaporization, flowing inert gasenriched in refrigerant from the auxiliary place of vaporization to aplace of absorption, evaporating a second refrigerant fluid in a placeof vaporization thermal ly segregated from the surroundings and alsosegregated from said first-mentioned place or places of vaporization toproduce refrigeration substantially free of frost formation, condensingthe second vaporized fluid at a place of condensation in thermalrelation with said region and returning condensate therefrom to saidplace of vaporization for second refrigerant fluid, intermittentlyeffecting rapid heating of said place or places of vaporization forfirst refrigerant fluid by a medium at a temperature level above theambient temperature of the surroundings to cause melting of any frostwhich may have been formed, the temperature of said place ofvaporization for second refrigerant fluid being substantially unaffectedby heated fluid received by said region or auxiliary place ofvaporization from said place or places of vaporization for firstrefrigerant fluid when heating of the latter is effected, and thermallysegregating said place of condensation and region in thermal relationtherewith from the surroundings and from said place of vaporization forsecond refrigerant fluid.

4. A method of refrigeration which includes evaporating a firstrefrigerant fluid in the presence of an inert gas in one or more placesof vaporization thermally segregated from the surroundings to producerefrigeration which may cause the formation of frost, flowing relativelycool inert gas enriched in refrigerant from the first-mentioned place orplaces of vaporization in a path of flow to a region removed therefromwhich is at a lower level and serves as an auxiliary place ofvaporization, flowing excess unevaporated refrigerant by gravity in suchpath of flow to said auxiliary place of vaporization from thefirst-mentioned place or places of vaporization, flowing inert gasenriched in refrigerant from the auxiliary place of vaporization to aplace of absorption, evaporating a second refrigerant fluid in a placeof vaporization thermally segregated from the surroundings and alsosegregated from said first-mentioned place or places of vaporization toproduce refrigeration substantially free of frost formation, condensingthe second vaporized fluid at a place of condensation in thermalrelation with said region and returning condensate therefrom to saidplace of vaporization for second refrigerant fluid, intermittentlysupplying a heated fluid to said place or places of vaporization forfirst refrigerant fluid to effect rapid heating of the latter and causemelting of any frost which may have been formed, the temperature of saidplace of vaporization for second refrigerant fluid being substantiallyunaffected by any heated fluid received by said region or auxiliaryplace of vaporization from said place or places of vaporization forfirst refrigerant fluid when heating of the latter is effected, andthermally segregating said place of condensation and region in thermalrelation therewith from the surroundings and from said plac ofvaporization for second refrigerant fluid.

5. In a refrigerator comprising a cabinet having segregatedcompartments, an absorption refrigeration system comprising a circuitfor inert gas including one or more cooling elements in whichrefrigerant fluid evaporates in the presence of an inert gas and anabsorber, at least one of said cooling elements being arranged toabstract heat from one of said compartments which serves as a freezerand may cause formation of frost due to the refrigerating effectproduced thereby, conduit means for conducting inert gas enriched inrefrigerant from said one or more cooling elements to said absorber,said conduit means including a conduit section intermediate saidabsorber and freezer into which enriched inert gas flows after leavingsaid one or more cooling elements, said conduit section being below saidfreezer and into which unevaporated refrigerant passes by gravity fromsaid one or more cooling elements, heating means operable to provide atsaid one cooling element, at a region removed from said conduit section,a medium which is at a temperature level above the ambient temperatureof the surroundings for rapidly heating said one cooling element tocause melting of any frost which may be formed, and a system for heattransfer fluid having a vaporization portion at one level arranged toabstract heat from another of said compartments and a heat rejectingportion at a higher level in heat conductive relation with said conduitsection, and means for thermally insulating said condensation portionand at least the part of said conduit section in heat conductiverelation therewith.

6. In a refrigerator comprising a cabinet having segregatedcompartments, an absorption refrigeration system including a gas circuitcomprising an absorber and one or more cooling elements in whichrefrigerant fluid evaporates in the presence of an inert gas, at leastone of said cooling elements being arranged to abstract heat from one ofsaid compartments which is employed for freezing purposes and may causeformation of frost due to the refrigerating effect produced thereby,conduit means for conducting inert gas enriched in refrigerant from saidone or more cooling elements to said absorber and into whichunevaporated refrigerant passes by gravity from said cooling element orelements, and a system for heat transfer fluid having a vaporizationportion arranged at one level to abstract heat from another of saidcompartments and a heat rejecting portion at a higher level in heatconductive relation with said conduit means, said refrigeration systemincluding a connection for conducting a heated fluid to said one coolingelement which is operable to cause melting of any frost which may beformed, means for controlling flow of such heated fluid through suchconnection, and means including insulation enveloping said condensationportion and at least the part of said conduit means in heat conductiverelation therewith.

7. In a refrigerator comprising a cabinet having segregatedcompartments, an absorption refrigeration system including a gas circuitcomprising an absorber and one or more cooling elements in whichrefrigerant fluid evaporates in the presence of an inert gas and conduitmeans for conducting inert gas enriched in refrigerant from the latterto said absorber, at least one of said cooling elements being arrangedto abstract heat from one of said compartments which is employed forfreezing purposes and may cause formation of frost due to therefrigerating effect produced thereby, a system for heat transfer fluidhaving a vaporization portion arranged at one level to abstract heatfrom another of said compartments and a heat rejecting portion at ahigher level in heat conductive relation with said conduit means, saidrefrigeration system including a connection for conducting warmabsorption solution to said one cooling element which is operable tocause melting of any frost which may be formed, means for controllingflow of such absorption solution through such connection, said conduitmeans serving as a path of flow for absorption solution from said one ormore cooling elements to said absorber, and means including insulationenveloping said condensation portion and at least the part of saidconduit means in heat conductive relation therewith.

8. In a refrigerator comprising a cabinet having segregatedcompartments, an absorption refrigeration system including a circuit forinert gas having one or more cooling elements in which refrigerant fluidevaporates in the presence of an inert gas and conduit means forconducting therefrom inert gas enriched in refrigerant and through whichunevaporated refrigerant passes by gravity from said cooling element orelements, at least one of said cooling elements being arranged toabstract heat from one of said compartments which serves as a freezerand may cause formation of frost due to the refrigerating effectproduced thereby, a system for heat transfer fluid having a vaporizationportion arranged to abstract heat from another ofusaid compartments anda heat rejecting portion in heat conductive relation with said conduitmeans, said refrigeration system including a connection for conductingto said one cooling element heated liquid having a higher boiling pointthan the refrigerant, such heated liquid being operable to cause meltingof any frost which may be formed, means for controlling flow of suchheated liquid through such connection, said conduit means also servingas a path of flow for such liquid which passes therethrough by gravityfrom said one cooling element, and means for thermally insulating saidcondensation portion and at least the part of said conduit means in heatconductive relation therewith.

SIGURD MATTIAS- BACKSTROM.

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